It is difficult to exclusively remove water from a mixture of an organic compound, such as alcohols, ketones and ethers, and water and purify an organic compound at high concentration only by normal rectification, since the mixture of water and an organic compound forms an azeotrope having a minimum boiling point.
Accordingly, as the method for exclusively extracting an organic compound at high concentration from a mixture of an organic compound and water, a method of removing a majority of water by distillation and thereafter, removing the remaining water by a pressure-swing adsorption apparatus (Pressure Swing Absorption; hereinafter, sometimes referred to as “PSA”) using an adsorbent has been proposed (see, Patent Document 1).
In addition, as the method for dehydrating a mixture of ethanol and water without enlarging the apparatus, a method of providing a membrane separation means to intervene between a vaporizer and PSA has been proposed. Furthermore, a method of supplying a purge gas discharged from PSA to a membrane separation means and obtaining high-concentration ethanol has been proposed (Patent Document 2).